For example, Japanese Patent Application Laid-Open Publication No. 2012-114644 (Patent Document 1) discloses a method of automatically setting LAG to a plurality of links which connect each interface relay and a plurality of fabric relays in a network relay system including the plurality of fabric relays and the plurality of interface relays. Japanese Patent Application Laid-Open Publication No. 2013-25505 (Patent Document 2) discloses a configuration in which a connection relation between the first level and the second level is different from a connection relation of a regular fat tree in a network device made up of switches having a three-level configuration connected by a fat tree. Japanese Patent Application Laid-Open Publication No. 2010-288168 (Patent Document 3) discloses a method in which each leaf switch transfers a packet received from a terminal to a specific route switch based on a destination address thereof and also transfers a learning packet to a specific route switch based on a source address thereof in a configuration including a plurality of leaf switches and a plurality of route switches relaying the communication therebetween.